The present invention relates to a valve for controlling flow of hydraulic fluid. The valve is used to control the flow of hydraulic fluid to a power steering motor.
A known power steering control valve for controlling flow of hydraulic fluid to a power steering motor includes a hollow valve sleeve and a valve core. The valve core is positioned within the valve sleeve. The valve core and the valve sleeve are relatively rotatable. Each of the valve core and valve sleeve has a plurality of lands and grooves.
When the valve core and valve sleeve are in a neutral position fluid is communicated to opposite chambers of the power steering motor at equal pressures. When the valve core and valve sleeve are relatively rotated from the neutral position, fluid flow is variably restricted. Restriction of the fluid flow causes pressurized fluid to be delivered to one of two chambers of a hydraulic power assist motor to cause motor actuation.
The restriction is provided by lands on the valve core and valve sleeve which define flow orifices. Variation of the flow orifices, and the amount of restriction, is provided by end surface segments of the lands which are formed such that varied amounts of relative rotation between the valve core and valve sleeve cause the end surface segments to be positioned at varying distances apart. Due to a high volume of hydraulic fluid flow and pressure differential changes as the hydraulic fluid flows through the flow orifices, noise may be created in the control valve.